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Transcript of Systems Thinking
Scientists call this simplified schematic -a model.
I bet you can think of a dozen ways to make this model more realistic. This is a picture of a McLaughlin Ridge in British Columbia, Canada. It is an example of a biome called a Temperate Rainforest.
Let's explore some of the generalized characteristics of a system, using the Pacific Northwest red cedar forest ecosystem as an example. This tree is an old growth red cedar tree. It is growing in a red cedar forest in the Walbran Valley on Vancouver Island, BC, Canada. The red cedar forest ecosystem is called this because red cedars are the dominant tree species. This specific tree is one of the largest trees in the valley. It is named the Tolkien Giant. It measures over 16ft in diameter at the base.
Photo care of Ancient Forest Alliance. Trees are one of the dominant components of forest ecosystems. There are lots of animal species in this system, too. Here are just a few.... System thinking requires that we think about how components interact with each other.
This "model" of a simple food chain illustrates the interactions between the sun, plants (producers), rabbits (herbivores), lynx (carnivores) and back to plants.
If you don't know these terms, don't worry, we will define them in the next lecture. There are lots of animals species in these systems, too. Here are just a few.... When components interact, they often do so in particular ways.
Through feedback loops.
Disturbance plays a role in ecological systems.
And, systems have emergent properties. A Positive feedback loop is when an increase in a particular variable leads to increases in a second variable which leads to increases in the first variable etc.
For example, temperate rainforest biomes are characterized by 200-350 cm of precipitation a year. That's a lot of moisture. Some of that moisture comes from the trees themselves as they transpire (move water from the ground to the atmosphere). Transpiration contributes to the formation of clouds and rain. Large tropical rainforests (and their humidity) generate as much as 75 percent of their own rain. The Amazon rainforest is responsible for creating as much as 50 percent of its own precipitation. Rain = more trees = more rain = more trees = more rain.
Another examples is birth contractions. Increases in hormones leads to stronger contractions and the release of more hormones which leads to stronger contractions etc. Negative feedback loops are when the state of one variable decreases a second variable.
For example, your thermostat is one of the most familiar examples. If you set your thermostat at 70 degrees, your furnace will turn on and increase the temperature in your house. When your house temperature reaches 71 degrees, your furnace turns off. The temperature in your house will then go down to 69 degrees. This will turn your furnace back on and the temperature will start to increase again.
Another example is predator-prey relationships - like our lynx and our rabbit. If there is a population explosion of rabbits, there will be a population explosion of lynx. The lynx will eat all the rabbits and then there will be no rabbits and the lynx will all die. Then the rabbit population will increase again and so on. Disturbance is a characteristic of a functioning ecosystem.
The definition of disturbance is any process that destabilizes or changes the system.
In ecological systems, disturbance usually returns a system to an earlier successional stage.
Humans have altered the intensity and frequency of disturbance in most systems. In the Pacific Northwest, volcanic eruptions are an example of a natural but infrequent disturbance. Mt. St. Helen erupted in 1980 and flattened thousands of acres of Pacific Northwest forests. This is a before and after view of Spirit Lake near Mount St. Helen Before After Humans also log forests in the Pacific Northwest. Logging these forests increases the frequency and scale of disturbance to these systems. Systems also have emergent properties. Emergent properties are simply properties that arise out of the system. It is the idea that a system is larger than the sum of its parts and has influences beyond its borders. An emergent property isn't any one part of the system, but a characteristic that arises out of all of the components working together.
A good example of an emergent property of a forest ecosystem is erosion control. These two images show mountain streams. One surrounded by intact forest. The other surrounded by logged forests.
Erosion control isn't any one part or component of the system. It is a service or function that arises out of the system. Temperate rainforests are found in the Pacific Northwest region of the North America. They are characterized by 200-350 cm of precipitation a year and temperatures that are on average above 0 degrees C and can seasonally reach as high as 20 degrees C. Don't know the difference between a biome and an ecosystem. That's OK. We'll learn this in the next two lectures. (Components) (Interaction) As you look at this and the next image, think about the fact that you are looking at all of these parts interacting together to "produce" a functioning ecosystem. But, keep in mind, this natural disturbance is truly infrequent in this system. Old Growth forests in the Pacific Northwest are thousands of years old. This means that they have existed without a large scale disturbance for a very long time. Photo: USFS from National Geographic - Spirit Lake These are pictures of Castle Grove in the Walbran Valley, B.C. This is an old growth red cedar forest. It is not all that different from the one that existed near Spirit Lake near Mount St. Helen. Photo courtesy of the Ancient Forest Alliance. Emergent properties Think for a minute. Make a list of other emergent properties of a forest ecosystem.
Hint: A phrase to consider when thinking about emergent properties is that the "whole is more than the sum of its parts." Climate control Now, when you look at a forest ecosystem, you should see the parts, their interactions and how those interactions add up to create a functioning system that has its own unique properties. All of the plants in the system interact to transpire moisture and create clouds which determines the climate of the region. Plant and animal Habitats The combination of plants and animals in a system can also create habitat for each other. For instance, old growth forests are habitat for marbled murrelets (an endangered bird species). Models help scientists ask questions and make hypotheses (predictions) about systems.
For instance, if we remove lynx, what might happen to the rabbits? Photo courtesy of the Ancient Forest Alliance